Fix Metal device edge cases; keep reporting the host GPU

From #61, without the default "AMD Radeon Pro 5500M" / 4 GB identity: the
host GPU's name and Vulkan working set stay the default for every app, and
the existing DARLING_METAL_GPU_NAME and DARLING_METAL_VRAM_MB overrides
remain the opt-in. Reporting 4 GB on a 2 GB card invites allocation
failures, and under-reports larger cards.

Kept from #61:
- registryID returns MTLDeviceInfo::kDefaultRegistryID instead of 0; a
  real Mac never reports 0 and apps key devices by it.
- Vertex buffer layout and attribute arrays release the old item after
  retiring it; the retire step read the item after the release could free it.
- newDepthStencilState, newSamplerState and the device name return nil (or
  the fallback name) when Indium throws, instead of unwinding through
  Objective-C.
- MTLDepthStencilGetIndium is declared only with DARLING_METAL_ENABLED.
- The replaceRegion trace probes at most `width` bytes, which stays inside
  the first row for every pixel format.

metal.patch is regenerated in its existing file order, so the diff is
these changes only. tests/test_metal_device_info.py compiles the host
check against MTLDeviceInfo.h as shipped in the patch and runs in CI.

Split from #61.

Co-authored-by: DevWebeloper <[email protected]>
Co-Authored-By: Claude Opus 5.5 <[email protected]>

.github/workflows/source-check.yml

@@ -17,3 +17,4 @@ jobs:
       - run: python -m unittest discover -s tests -p 'test_hidden_riot_recovery.py'
       - run: python -m unittest discover -s tests -p 'test_desktop_run.py'
       - run: python -m unittest discover -s tests -p 'test_urlsession_runner.py'
+      - run: python -m unittest discover -s tests -p 'test_metal_device_info.py'